A dispenser device for granular material is disclosed for example in the U.S. Pat. No. 2,852,170 issued in 1958 to Edward Reynolds. In this patent, there is provided an measuring or loading chamber 10, and two valves 17, 22, adapted to selectively close the inlet and outlet ports of the loading chamber. Valves 17, 22, are actuated by a push rod 18, and biased by two coil springs 25, 30, in relation to the closing/opening of the chamber ports, spring 25 always remaining within chamber 10 while spring 30 normally partially engages this chamber. The capacity of measuring chamber 10 can be adjusted by screwing or unscrewing lower port 31.
One major disadvantage of such a construction is that the range of capacity of adjustment is very limited due to the valving arrangement. Another disadvantage is that the powder will quickly come to clog both springs 25 and 30 (and especially spring 25) and thus impair their efficiency. It may further have a contaminant effect with respect to the powder. Moreover, in the position of FIG. 4, where the valves 17 and 25 abut against each other in the final powder dispensing step, powder may very well become trapped within the small chamber defined by the two registering cavities made in the valves 17 and 25, so that the amount of powder falling through the lower port 23 may vary from dispensing stroke to dispensing stroke. Also, the upper port of the chamber being counterbored for providing a seat for the upper valve, this is disadvantageous because it is prone to rapid wear.